The specific aims of this proposal are: 1) to develop a prosthetic system for the replacement of bone segments and joints after tumor resection, 2) to apply bone in-growth material to the prostheses for prolonged fixation without bone cement, 3) to quantitate patients' joint functional changes due to such resection and reconstruction, and 4) to establish better therapeutic and rehabilitation programs for functional improvement and prosthesis protection. In cancer amputees, effective gait training methods will be developed to improve functional recovery. Their results will be compared to those with tumor implants for objective assessment of treatment efficacy. The design of the implant system with interchangeable modular units to accommodate patient and surgical variations will involve bone cross-sectional analysis, stem optimal design, and in vitro tests. The anatomical regions of resection and replacement include the femur, the tibia and the humerus, with or without involvement of a joint. A large cancer patient population with proper indications will be studied. Their clinical and functional results will be followed. For lower extremity reconstruction, gait analysis will be performed. Patients with upper arm involvement will be studied using a video system. A modified CYBEX II machine will be used to obtain isometric and isokinetic joint strengths. Results are summarized and graphed by a computer to prepare a physician's report. Gait training will be conducted with simple and effective biofeedback devices. The long-term objectives are to develop an effective and reliable system of prosthetic devices to replace the resected bone and joint and to monitor function of these patients to ensure their lasting good results. Booklets will be developed to educate these patients. The experience and knowledge gained here can benefit failed total joint arthroplasties. This project represents a total integration of several disciplines. With a dramatic improvement in the prognosis of various types of malignant bone and soft tissue tumors and with increased interest in limb saving resections for these tumors, the present techniques can provide the best functional results in a large group of cancer patients.